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Platelet Thrombus Formation and Hemostasis Are Delayed in the Microcirculation of Copper-Deficient Rats^{1, 2, 3,}

Center for Applied Microcirculatory Research, University of Louisville, Louisville, KY 40292 ^* U.S. Department of Agriculture, Agricultural Research Service, Grand Forks Human Nutrition Research Center, Grand Forks, ND 58202

The role of dietary copper in platelet thrombus formation and hemostasis was studied in the cremaster muscle microcirculation. Male weanling Sprague-Dawley rats were fed purified diets that were either copper-adequate (94 µmol Cu/kg diet) or copper-deficient (0 µmol Cu/kg diet) for 1, 3 or 5 wk. The rats were anesthetized with pentobarbital, and the cremaster was spread in a Krebs-filled tissue bath. Fluorescein isothiocyanate tagged to bovine serum albumin (FITC-BSA) was injected intra-arterially. After a 20-min equilibration, blue light (1.8 W/cm², 450–490 nm) was used to activate the FITC-BSA and induce platelet thrombus formation within the vasculature. In vivo television microscopy was used to quantify the thrombus formation. In rats fed the copper-deficient diet for 3 or 5 wk, platelet thrombus formation induced by photoactivation was significantly (P < 0.05) delayed and prothrombin time was significantly longer but the number of circulating platelets was significantly greater than in age-matched rats fed the copper-adequate diet. Bleeding time, measured after micropuncture of a second-order venule, was significantly longer but hematocrit was significantly lower in rats fed the copper-deficient diet than in those fed the copper-adequate diet. The results demonstrate that platelet-mediated hemostasis is depressed in dietary copper deficiency and that this may be due to a decrease in hematocrit, a decrease in the activity of a coagulation factor and/or an alteration of platelet function.

KEY WORDS: • copper • rats • platelets • microcirculation • hemostasis

¹ This material is based upon work supported by the Cooperative State Research Service, U.S. Department of Agriculture, under agreement no. 92-37200-7676.

² Mention of a trademark or proprietary product does not constitute a guarantee or warranty of the product by the U.S. Department of Agriculture and does not imply its approval to the exclusion of other products that may also be suitable.

³ The costs of publication of this article were defrayed in part by the payment of page charges. This article must therefore be hereby marked "advertisement" in accordance with 18 USC section 1734 solely to indicate this fact.

⁴ To whom correspondence and reprint requests should be addressed.

Manuscript received 18 October 1993. Revision accepted 15 February 1994.